Electrical power coupling systems for roadways have been known for many years. Trolley busses have been in use since the early 1900's which utilize associated flexible booms having at their distal ends power pickoff arrangements for drawing power from overhead power cables supported from buildings or poles. Such trolley busses have many benefits in urban surroundings, for example low operating noise, low air pollution at the trolley busses, fast acceleration and relatively simple drive trains in the trolley busses themselves. However, considerable maintenance is required for the overhead power cables, for example on account of arcing which occurs when the power pickoff arrangements are moved relative to the overhead power cables when in operation. On account of such practical difficulties, inductive power coupling systems for roadways have been described earlier in published literature as being a possible solution for future transport infrastructure.
In a United Kingdom patent no. GB 1418128 published in December 1975 (“Improvements in or relating to electrified transportation”, Otto), there is described an electrical supply arrangement for an electrically driven vehicle, wherein the supply arrangement comprises one or more current carrying conductors which are external to and separate from the vehicle. The one or more conductors are operable to provide an induced inductive electrical supply in at least one electrical circuit located in or on the vehicle so as to drive the vehicle. The electrical circuit comprises one or more inductive and one or more capacitive elements in series, and are integrally formed as a sandwich arrangement of two or more electrically conducting members and one or more electrically insulating members. Optionally, the frequency of the electrical supply to the one or more current carrying conductors is at, or close to, the resonant frequency of the electrical circuit. Optionally, the electrical circuit is formed in an integral manner from one or more series-connected sandwich arrangements of highly-conducting metal strips and very low loss dielectric strips. More optionally, the or each integrally-formed circuit of capacitive and inductive elements has a resonant frequency at or close to the supply frequency of the current flowing through the one or more current carrying conductors. In an example described in the patent, a 6 kW power transfer is described at a resonant frequency of 7.5 kHz. Such power transfer is insufficient to meet contemporary power requirements for electric vehicles which often employ electric drive trains with electric motors of 10 kW or greater. Contemporary hybrid electric trucks often employ traction motors of up to 100 kW rating.
In a published European patent application no. EP 0 289 868A2 (“Roadway power and control system for inductively coupled transportation system”, Inductran Corporation, published November 1988), there is described an electrical modular roadway system which is operable to transmit power to and to control inductively coupled vehicles travelling thereon. The system comprises a plurality of elongate, electrically connected inductor modules arranged in an aligned end-to-end spaced apart for forming a continuous vehicle path. Each module has a magnetic core and power windings which generate a magnetic field extending above the road surface. Controllable relays are connected between the modules for allowing operating electric current to either activate or bypass selected modules. Moreover, sensing windings in the modules are activated by the presence of a vehicle on one module to provide control signals to relays for other modules. The patent application does not mention operating frequency, but it is implicit that this operating frequency is electrical power line frequency of circa 50 Hz or 60 Hz in view of ferromagnetic core materials needing to be employed. The system does not appear to have come into general widespread use, presumably in view of major road works being required to install the modules.
In a granted German patent no. DE 4429656C1 (“Einrichtung zur berührungsfreien Ûbertragung elekrischer Energie auf einen Gegenstand”, Professor Meins) published in April 1996, there is described a resonant inductive energy coupling system for road vehicles, wherein the system employs inductive coupling coils with series resonant capacitors.
Despite being proposed on many occasions in earlier patent applications and granted patents, wireless inductive power coupling for road vehicles has not been generally adopted within contemporary transport infrastructure. A reason for such lack of adoption may arise on account of high initial installation cost of road-embedded inductive coils and low petroleum prices. However, with an onset of “peak oil” and concerns regarding potential anthropogenic climate change associated with Carbon Dioxide emissions, interest has been recently reawakened in respect of such inductively-coupled roadways, especially when many new designs of road vehicles are now being based upon plug-in hybrid drive train configurations. However, there still arises a need for an optimal internationally standardized configuration of inductive power transfer system for roadways before major investments are likely to be implemented. The present invention seeks to address the aforementioned problems associated with known technical art to render possible practical inductive power transfer systems for roadways and electric vehicle which are compatible therewith.
Many demonstrations of supplying electrical grid power to moving vehicles have been made. Most demonstrators that have been implemented in practice involve guided vehicles, for example trams, light rail and trains, or vehicles with restricted movement such as trolley busses. Inductively powered roadway systems have been proposed for powering trams, and, to a lesser extent, busses; for example a system was proposed some years ago by Bombardier. Despite successful operation of these systems, they have not been adopted into road vehicle applications, primarily on account of major infrastructure changes required and corresponding installation of vehicle fitments.
Electrical roadway systems have been known for many years. Trolley busses have been in use since the early 1900's which utilize associated flexible booms having at their distal ends power pickoff arrangements for drawing power from overhead power cables supported from buildings or poles. Such trolley busses have many benefits in urban surroundings, for example low operating noise, low air pollution at the trolley busses, fast acceleration and relatively simple drive trains in the trolley busses themselves. However, considerable maintenance is required for the overhead power cables, for example on account of arcing which occurs when the power pickoff arrangements are moved relative to the overhead power cables when in operation.
In the foresaid electrical supply arrangement of GB 1418128, it is found in practice that mounting a resonant power coupling arrangement onto an underside of a vehicle reduces access to other vehicle parts from the underside of the vehicle. Such access is important when the vehicle is a hybrid vehicle which includes a combustion engine system for generating motive power from carbonaceous fuel oxidation, wherein combustion gases are directed in operation via an exhaust system having an exhaust pipe mounted underneath the vehicle. Removing the resonant power coupling arrangement for gaining access to the exhaust pipe is time consuming. Moreover, a resonant power coupling apparatus which covers the underside of the vehicle results in impaired cooling to the exhaust pipe. Moreover, implementing the resonant power coupling apparatus to occupy less area reduces a performance of the apparatus to couple power for gaining access the exhaust pipe.
Electrical roadway systems have been known for many years. Trolley busses have been in use since the early 1900's which utilize associated flexible booms having at their distal ends power pickoff arrangements for drawing power from overhead power cables supported from buildings or poles. Such trolley busses have many benefits in urban surroundings, for example low operating noise, low air pollution at the trolley busses, fast acceleration and relatively simple drive trains in the trolley busses themselves. However, considerable maintenance is required for the overhead power cables, for example on account of arcing which occurs when the power pickoff arrangements are moved relative to the overhead power cables when in operation.
In the foresaid electrical supply arrangement of GB 1418128, it is found in practice that a relatively small clearance has to be employed between an upper surface of a roadway in which excitation coils are housed and a pickup coil mounted to an underside of a vehicle which is operably compatible with the roadway. Such a relatively small clearance, for example in a range of 10 cm to 20 cm, potentially represents a safety hazard when vehicles are travelling a high speeds, for example 120 km/hour, upon the roadway, especially when there is a risk of loose objects, namely debris being present on the upper surface of the roadway. Such loose objects risk being wedged under the vehicles and damaging their respective pickup coil. A conventional manner to address this risk is to employ larger clearances and increase an area or number of turns included on the pickup coil, but potentially adds considerably to cost.
Despite the aforementioned wireless-powered electrical supply arrangement being described in December 1975, the arrangement has not been adopted into general use, presumably on account of petroleum being plentiful and there being little impetus to employ alternative vehicle propulsion technologies.
Electric vehicles for use with electrical roadway systems have been known for many years. Trolley busses have been in use since the early 1900's which utilize associated flexible booms having at their distal ends power pickoff arrangements for drawing power from overhead power cables supported from buildings or poles. Such trolley busses have many benefits in urban surroundings, for example low operating noise, low air pollution at the trolley busses, fast acceleration and relatively simple drive trains in the trolley busses themselves. However, considerable maintenance is required for the overhead power cables, for example on account of arcing which occurs when the power pickoff arrangements are moved relative to the overhead power cables when in operation.
A problem with the electrical supply arrangement described in aforesaid patent no. GB 1418128 is that a relatively close spacing is required to be maintained between the one or more current conductors which are external to and separate from the vehicle relative to the at least one electrical circuit located in or on the vehicle for driving the vehicle. In an event of road debris or occluding material, for example snow, being present upon a road surface above the one or more current conductors, there arises a risk of the road debris or occluding material damaging an underside of the vehicle, for example causing damage to the one or more conductors. When high vehicle speeds are employed, for example greater than 50 km/hour, the road debris or occluding material can potentially cause accidents. Conventionally, careful maintenance of roadways to remove the road debris or occluding material would be considered necessary, but such maintenance is not economically feasible to achieve in practice for all sections of road equipped with the one or more current conductors.
When the electrical supply arrangement is evolved to a form suitable for delivering 10 kW of more, for example 50 kW, for propelling contemporary electrical vehicles, or electric-hybrid vehicles including chemical oxidation processes for providing a source of energy for motive power, the aforesaid electrical circuits are excited with considerable signal magnitudes and associated alternating currents such that safety issues then need to be taken seriously into account. Safety issues can relate to one or more of the following:    (a) exposure of personnel to high-power alternating electromagnetic fields which can potentially represent a biological hazard;    (a) electrical shock risk to personnel when circuit cable windings embedded into a roadway are faulty or damaged, resulting in a breakdown of cable insulation;    (b) corrosion causing damage to conductors of circuit cable windings embedded into the roadway, resulting in an increase in cable resistance and associated resistive power losses when excited in operation, namely losses which are potentially spatially concentrated and can result in fire risk by setting adjacent asphalt and/or cable insulation into combustion; and    (c) gross roadway surface damage which can potentially result in circuit cable windings being severed and exposed at a surface of the roadway, representing an electrical shock hazard, for example as a consequence of Earthquake, road subsidence or major road accident.
Although such safety issues can potentially be addressed, at least in part, by human inspection of roadways, it is desirable to employ more robust and less personnel-intensive approaches to ensure safety of electrical roadways employing inductive power transfer to vehicles.
In a published European patent application no. EP 0,289,868 (“Roadway power and control system for inductively coupled transportation system”, Inductran Corporation, California, USA), there is described an electrical modular roadway adapted for transmitting power to and controlling inductively-coupled vehicles travelling thereon. The system comprises a plurality of elongate, electrically-connected inductor modules arranged in an aligned end-to-end spaced apart manner in order to form a continuous vehicle path. Each module has a magnetic core and power windings which generate a magnetic field extending above the road surface. Controllable relays are connected between modules for allowing operating electric current to either activate or bypass selected modules. Sensing windings included in the modules are activated by the presence of a vehicle on one module to provide control signals to relays for other modules. Although an operating frequency for creating the magnetic field is not described, the modules are constructed in a manner which would allow them to be energized at normal line frequency, for example 50 Hz or 60 Hz.
The aforesaid electrical supply arrangement (Otto) and the aforementioned roadway power and control system (Inductran Corp.) potential represent a major installation task when being retrofitted to existing roadways. For example, the aforementioned roadway power and control system requires a major trench to be prepared along vehicle-bearing lanes of a roadway for accommodating the modules, including their magnetic cores. Moreover, the aforesaid electrical supply arrangement requires a complex configuration of coil windings to be installed in a roadway which is costly and time consuming. Such cost and complication represent a technical problem which dissuades implementation of inductively-coupled vehicle roadways, thus favouring contemporary alternatives such as continuing to employ Carbon-fuel driven vehicles and/or to employ vehicles with large heavy rechargeable batteries, for example sealed Lead-acid accumulators which are environmentally damaging and Lithium batteries which represent a potential fire risk.
Concerns regarding “peak oil” and anthropogenic forcing of climate change require that road transport in future be evolved away from burning of fossil fuels. Moreover, resource limitations on battery materials, for example World supply of Lithium, prevents a majority of road vehicles in the World being implemented as electric rechargeable vehicles. Furthermore, heavy rechargeable batteries in road vehicles is undesirable from a safety viewpoint on account of kinetic energy KE in the road vehicles being given by ½ mV2, wherein m is a mass of the vehicle, and V is a velocity of the vehicle when in motion. For example, a contemporary Tesla Roadster vehicle is a very highly regarded and respected quality product and includes a Lithium rechargeable battery having a mass in an order of 500 kg; at a speed of 100 km/h, such a Roadster vehicle has a kinetic energy in an order of 500 kJ which is potentially instantaneously released in an event of a severe crash situation. Similar considerations pertain also to other types of contemporary electric and hybrid vehicles.
There thus arises a problem of implementing an inductively-coupled roadway for providing motive power to electric and hybrid vehicles in a manner which is commercially more attractive and more straightforward to implement in comparison to known arrangements and systems.
As World population increases from presently 7 billion people to around 10 billion people by year 2050, Earth's resources are being shared between increasingly more people, especially as living standards improve in Asia, in particular China and India. Energy-per-capita based upon known oil and gas reserves falls rapidly from year 2020 onwards. On account of metals requiring considerable energy in their mining, processing and adaptation into products such as electrical cables, transformers and weatherproof housings for example, it is anticipated that metal thefts will become a major problem in the future. When such theft concerns infrastructure such as cables along sides of railway tracks, theft of such cables for their metal content can be highly disruptive to reliable operation of such infrastructure. Moreover, damage caused by hasty cable thefts can be very costly to repair, often much more costly than merely metal value of the cables themselves.
In an event that electrical roadways are developed to provide contactless inductive transfer of motive power to electrically-propelled vehicles, for example as described in aforesaid United Kingdom patent no. GB 1418128, a problem potentially arises when cables embedded into road surfaces for implementing such roadways are stolen on account of their scrap metal value. A conventional approach would be to employ an army of roadway policemen and roadway policewomen in situ to keep watch of roadways, namely to arrest promptly any thieves who attempt to steal roadway-embedded cables; such an approach would be extremely expensive, although it could assist to reduce contemporary unemployment in a post “peak-oil” society. Alternatively, another conventional approach would be to provide surveillance equipment along roadways, for example surveillance cameras, coupled to a centralized security facility with rapid-deployment policemen and policewomen to travel out and arrest thieves in an event of cable theft being detected. A yet alternative conventional approach would be to embed the cables is such a mechanically secure manner into roadways that theft would be difficult to undertake by unauthorized parties. However, such secure embedding of cables renders them difficult to access in an event that authorized parties are required to replace or to repair the cables. Moreover, operating surveillance equipment is costly in personnel time, wherein personnel remotely monitor surveillance camera images for traces of theft or potentially thieving activities.